Hi,
That's the normal behavior and is quite common.
When data is posted to the server and that the server replies with a page display, if you use the history of your browser, most recent browsers will display an alert page with a link to resubmit the data and you need to click on the link to see the page.
The mechanism has been added by web browsers several years ago to prevent users from submitting several times the same stuff (to avoid duplicate credit card payments for example).
A solution you can use if you don't want that is to add such line:
if ($config->get('redirect_post',1) && $_SERVER['REQUEST_METHOD'] === 'POST' && (empty($this->module) || JRequest::getVar('hikashop_front_end_main',0))) {$app->redirect(hikashop_currentURL());}
after the code:
$dispatcher->trigger( 'onBeforeProductListingLoad', array( & $filters, & $order, & $this, & $select, & $select2, & $a, & $b, & $on) );
of the file components/com_hikashop/views/product/view.html.php so that there will be a redirect to the current page after the post data has been saved in the session and avoid that behavior.